LordOfTheFlies was gracious enough to translate the webchat system messages for us, and he mentioned that we might double check with some native speakers, so here are the English and Japanese versions to compare.

Can any native/fluent speakers double check this and let us know if it's good enough? Thank you!

(For instance we were wondering whether it was better to use 報告 rather than 忠告 given that we just want to give the user a reason to explain something, rather than necessarily warn them? )

'userJoinedRoom' : '%s joined the room.',
'userLeftRoom' : '%s left the room.',
'userHasBeenKickedFromRoom': '%s has been kicked from the room.',
'userHasBeenBannedFromRoom': '%s has been banned from the room.',

<geektalk>
I've fixed up the translation and submitted it.. but for now with the caveat that they can't really use it until a certain functionality is added to one of the libraries they're using... the jquery-i18n (internationalization plugin). Currently it doesn't allow you to reorder the string variables, which we need to do to swap around the username and roomname on the "kick" and "ban" messages to have them sound correct in Japanese.

One of the webchat developers has submitted a bug report to the jquery-i18n developer to get it fixed, but said that he'll probably just fix it himself since the webchat developers will kind of be relying on it to allow other translations that might also have a different word order than English.
</geektalk>

That's all I can do with that for the moment. Back to work on other things!
(I also finished ironing out the bugs from Rich's Yuki manga pages tonight! (I hope!) I feel productive. )